Photocatalytic degradation of phenol by semiconducting mixed oxides derived from Zn(Ga)Al layered double hydroxides

• ZnAl and ZnGaAl layered double hydroxides with varying molar ratios were prepared.
• Solid solutions obtained by calcination possess semiconducting properties.
• 80 and 40 ppm of phenol were photocatalytically degraded.
• Maximum degradation was ca. 80% in 6 h.

The synthesis and characterization of ZnAl and ZnGaAl layered double hydroxides and the mixed oxides derived from their calcination is presented. The semiconducting properties of the mixed oxides were analyzed by DR-UV–Vis. It was found that all mixed oxides are semiconductors with band gaps close to that of ZnO. Also, substitution of Al3+ for 5 or 10% wt. of Ga3+ decreases the band gap below that of ZnO, despite the fact that gallium oxide is a wide band gap semiconductor. Then, the photodegrading capabilities of the mixed oxides were tested using phenol, a very recalcitrant compound, as a probe. Nearly 80% of initial 40 ppm and 60% of initial 80 ppm of phenol were degraded in 6 h over ZnAl-3 and ZnGaAl-5% photocatalysts.

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